The present invention relates generally to the field of battery compartments for small electronic devices. More particularly, the present invention relates to a battery compartment and door wherein the battery is supported on a flexible strap and where the strap also forms a living hinge for the compartment door.
Enclosures for button-type batteries for miniature electronic devices, such as hearing aids, present a number of design challenges. Batteries for these devices are necessarily small and difficult to manipulate. A battery compartment that simplifies the task of changing batteries is desirable.
The overall size of the hearing aid must be small to provide acceptable user comfort and esthetic appearance. It is therefore desirable that the battery enclosure itself occupy a minimum volume. Structures that serve dual purposes are also desirable since this reduces the number of parts required and has a positive impact on the size of the device.
Known methods of forming battery compartments for miniature electronic devices suffer from a number of defects. Typically a door is provided on the surface of the device that admits a button battery into a chamber. The battery is forced edge-wise into the chamber and spring electrodes press the faces of the battery to supply power to the device.
A high force applied by the spring electrodes is desirable, since this increases the reliability of the electrical contact between the battery and the electrodes. Also, a high spring force improves the wiping action of the springs against the battery, thereby removing dirt and corrosion between the battery and the electrodes.
Such a high spring force creates a problem, however, and removal of a drained battery from the compartment is difficult because the battery is held tightly between the springs. The batteries typically used for this kind of application are quite small and difficult to grasp. Extraction is frequently accomplished by the so-called "rapid deceleration" method, that is, by slamming the device against the user's palm. Such treatment of expensive electronic equipment is less than desirable.
Another method of providing a battery enclosure is to form an opening in a surface of the hearing aid large enough to admit a button battery face first. A spring electrode is provided at the bottom of the opening. A door, usually including a second spring electrode, is then locked down on top of the battery.
This method solves the problem of battery extraction but introduces other problems. A relatively large door must be provided, increasing the device size. The door must include an electrical connection to the electrode, as well as a locking mechanism. This increases the complexity of the door, and makes the device more difficult to manufacture and less reliable.
An alternative method for inserting and extracting a battery from a small electronic device edge-wise is illustrated in U.S. Pat. No. 3,138,491 (Rubio). A frame is provided with an opening to accommodate the circumference of a button battery. One corner of the frame is hinged so that the frame rotates into the electronic device. A battery is placed within the frame and is carried edge-wise into the device between internal spring electrodes as the frame rotates into the device. When the frame is fully rotated into the device an exposed side of the frame forms the battery compartment door. A tab extends from the door. To remove the battery the user grasps the tab and rotates the frame out of the body of the device. The frame pulls the battery from between the electrodes.
The Rubio device solves the problem of extracting the battery. It is not ideal, however, because it requires a relatively complicated mechanism to form the battery compartment. Also, the frame and hinge must be accommodated within the device, which adversely impacts on the overall size of the device. In addition, the battery must be held in the frame by the user as the door is closed. The small sizes of the battery and the frame make this difficult.